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This invention relates to rendering a non-photorealistic (xe2x80x9cNPRxe2x80x9d) image from an original model.
NPR rendering is a process in which a three-dimensional (xe2x80x9c3Dxe2x80x9d) model is rendered as a two-dimensional (xe2x80x9c2Dxe2x80x9d) image with shading that is non-photorealistic. There are many methods of rendering non-photorealistically. One of these methods produces a 2D cartoon-like effect, in contrast to photorealistic shading, such as gouraud or phong shading, which produces a 3D effect.
Traditional animation techniques involve drawing 2D images on cels, often by hand. Each time a new perspective of the original 3D model is required, an entirely new image is drawn on a new cel. Recently, computers have been used in the animation process.
In general, in one aspect of the invention, a method for use in rendering an NPR image from an original (e.g., 3D) model, selects a normal in the original model and substitutes a vector for the normal to produce an NPR image corresponding to the original model.
Among the advantages of the invention are one or more of the following. Substituting vectors for normals in the NPR image alters the shading of the NPR image. For example, the shading of the NPR image can be altered so that the image does not appear photorealistic. NPR images, such as cartoon images, can thus be rendered and shaded for any perspective of the original model. For example, an original model can be positioned, and a shaded NPR image rendered for that position. The original model can then be repositioned and a shaded NPR image rendered for the new position.
Other advantages and features will become apparent from the following description and the claims.